When you’ve been at the top of anything in rank, did you think down was the only way you could go from there? Do you think most champions, and people at the top of any level, in anything, think down is the only way they could go from there?
Down being the only way to go from the top is only true if you carried a very narrow perspective. If you even considered staying at the top until stepping away on your terms, like retirement or moving on while still champion, to be a goal worthy of pursuit, it would be a metaphorical destination that is an alternative to going down. Also, when at the top, why can’t you redefine what being there means? You could push that top to new heights, or add more accomplishments not expected of it, like winning championships in multiple weight divisions in boxing, or in multiple sports.
There’s no reason to think that down is the only way to go when at the top. To do so would leave you with a contradictory mindset than that possessed on the way up. You’d always be looking down in fear of being knocked off the top instead of always looking up in aspiration that is far more enjoyable. No. When at the top, continually remind yourself that down is not the only way you could go from there, to help you not only stay there, but also to push limits for what it could mean to be at the top!
As for the physical interpretation of where you can go when at the top, note that there is no top to the sky. You can go up forever. You just can’t climb there. You can get to the top in many ways, but you can only fly to the stars.